## MapContains

You have been assigned the task of implementing a product inventory using Java maps. Each product has a unique ID as the key and the corresponding product details as the value.

### Instructions

Create a file `MapInventory.java`.

Write two functions:

Write a function `getProductPrice` that takes in parameters a map of product IDs and their corresponding prices, along with a product ID, and returns the price of the specified product. If the product ID is not present in the map, the function should return `-1`.

Write a function `getProductIdsByPrice` that takes a map of product IDs and their corresponding prices, along with a price as parameter, and returns a list of product IDs that have the given price. If no products are found for the specified price, the function should return an empty list.

### Expected Functions

```java
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

public class MapInventory {
    public static int getProductPrice(Map<String, Integer> inventory, String productId) {
        // your code here
    }

    public static List<String> getProductIdsByPrice(Map<String, Integer> inventory, int price) {
        // your code here
    }
}
```

### Usage

Here is a possible ExerciseRunner.java to test your functions:

```java
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class ExerciseRunner {

    public static void main(String[] args) {
        Map<String, Integer> inventory = new HashMap<>();
        inventory.put("P001", 100);
        inventory.put("P002", 50);
        inventory.put("P003", 75);
        inventory.put("P004", 50);
        inventory.put("P005", 75);

        System.out.println(MapInventory.getProductPrice(inventory, "P002")); // Output: 50
        System.out.println(MapInventory.getProductPrice(inventory, "P004")); // Output: 50
        System.out.println(MapInventory.getProductPrice(inventory, "P006")); // Output: -1

        List<String> productsWithPrice50 = MapInventory.getProductIdsByPrice(inventory, 50);
        System.out.println(productsWithPrice50); // Output: [P002, P004]

        List<String> productsWithPrice75 = MapInventory.getProductIdsByPrice(inventory, 75);
        System.out.println(productsWithPrice75); // Output: [P003, P005]

        List<String> productsWithPrice80 = MapInventory.getProductIdsByPrice(inventory, 80);
        System.out.println(productsWithPrice80); // Output: []
    }
}
```

and its output :

```shell
$ javac *.java -d build
$ java -cp build ExerciseRunner
50
50
-1
[P002, P004]
[P003, P005]
[]
$
```

### Notions

[Map](https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/Map.html)
[List](https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/List.html)